Revert^2 "Make Lint FlaggedApi violations errors"

This reverts commit 38813efb534577a1c4cbe995fd2854ed30c5f0a7.

Reason for revert: all known Lint violations baselined.

Change-Id: Ic6bf778df563ef6a592427442a9cc6a3d9ef8b51
diff --git a/java/lint_defaults.txt b/java/lint_defaults.txt
index b8ce95c..262e184 100644
--- a/java/lint_defaults.txt
+++ b/java/lint_defaults.txt
@@ -123,9 +123,6 @@
 --warning_check SupportAnnotationUsage
 --warning_check UniqueConstants
 --warning_check UseSdkSuppress
-# TODO(b/303434307) The intent is for this to be set to error severity
-# once existing violations are cleaned up
---warning_check FlaggedApi
 
 --warning_check ExactAlarm
 --warning_check ExpiredTargetSdkVersion